1. Field of the Invention
The present invention relates to an organic electroluminescent device and a method of fabricating the same
2. Description of the Background Art
Organic electroluminescent devices (hereinafter referred to as organic EL devices) are new self-emitting devices of great prospect. Such organic EL devices have a stacked structure in which a carrier transporting layer (an electron transporting layer or a hole transporting layer) and a light emitting layer are formed between a hole injecting electrode and an electron injecting electrode.
As a material of the hole injecting electrode, an electrode material having a large work function such as gold or ITO (indium-tin oxide) is used, whereas as a material of the electron injecting electrode, an electrode material having a small work function such as Mg (magnesium) or Li (lithium) is used.
Moreover, organic materials are used for the hole transporting layer, the light emitting layer, and the electron transporting layer. A material having the property of a p-type semiconductor is used for the hole transporting layer, and a material having the property of an n-type semiconductor is used for the electron transporting layer. The light emitting layer is composed of an organic material having carrier transportability such as electron transportability layer and hole transportability and emitting fluorescence or phosphorescence.
Each functional layer, that is, the hole transporting layer, electron transporting layer, and light emitting layer, can be composed of a plurality of layers, or be omitted, depending on the organic materials used.
In order to improve the operating stability of such organic EL devices, it has been proposed that a CuPc layer (copper phthalocyanine) be interposed between the hole injecting electrode and the hole transporting layer. However, interposing the CuPc layer actually has the disadvantage of increasing the operating voltage. In an attempt to enhance the hole injectability and to improve the operating stability, an organic EL device where a polymer thin film of fluorocarbon synthesized by RF (radio frequency) plasma polymerization method is interposed between the hole injecting electrode and the hole transporting layer has been proposed (e.g. see JP 2000-150171 A).
However, the above conventional organic EL device exhibits degraded heat-resistance due to the interposition of the polymer thin film between the hole injecting electrode and the hole transporting layer.